States that were leaders in childhood vaccination before the pandemic are among those losing ground as exemptions and unfounded skepticism take hold, encouraged by the Trump administration’s stance under U.S. Health and Human Services Secretary Robert F. Kennedy Jr. As childhood vaccination decreases, the risk of disease for vulnerable populations rises.

Expanded exemptions for parents are likely to drop both Mississippi and West Virginia from the top national rankings they held before the pandemic, according to a Stateline analysis of federal data. Other states like Florida, Idaho, Louisiana and Montana also are pushing the envelope on vaccine choice.

At least 33 states were below herd immunity in the 2024-25 school year, compared with 28 states before the pandemic in 2018-2019, the analysis found. Herd immunity refers to the percentage of people who must be vaccinated or otherwise immune from an infectious disease to limit its spread.

Research shows that in the case of measles — a highly contagious disease — states need to maintain at least 95% vaccination rates to protect people who can’t get vaccinated. Other diseases have similar herd immunity rates. People who can’t be vaccinated might include infants too young to receive certain vaccines and those with underlying health conditions.

Misinformation and expressions of distrust from influential leaders have an effect on parents, doctors say, as do new state exemptions making it easier for families to avoid the vaccines, contributing to childhood vaccination decreases.

Some people who never questioned vaccines before notice a national debate and get confused, said Dr. Patricia Tibbs, a pediatrician in rural Mississippi and president of the Mississippi chapter of the American Academy of Pediatrics. New religious exemptions may already be fueling an increase in pertussis, also known as whooping cough, in Mississippi, she said.

“If they hear something about it in the news, then it must be right, they think,” Tibbs said. “We’re just following the guidelines and informing patients that this is a scientific discussion. Nothing has changed about the science. But people who don’t know science are making decisions.”

Read the full article about childhood vaccination rates decreasing by Tim Henderson at Stateline.